This invention relates generally to torque transmission apparatus and, more particularly, to a mechanical clutch apparatus of the stepless type.
Couplings and clutches for the transmission of torque from driving to driven shafts are well known. Such known couplings or clutches may be mechanical, hydraulic or electrically actuated. More particularly, mechanical clutches and couplings may be grouped into certain classes, such for example, as fixed couplings, moving couplings, elastic couplings, disengagement clutches and self-actuating clutches.
With respect to fixed couplings, the most common type utilizes a bolted flange coupling for interconnecting the driven to the driving shaft. With respect to moving couplings, the most common are geared couplings, spherical couplings, universal joint couplings and Cardan joints. Elastic couplings are generally similar to fixed couplings of the flange type wherein in lieu of the bolted flange connection, an elastic connection, such as a rubber sleeve, is utilized to interconnect the shafts.
The most common types of disengaging clutches include so-called dog clutches and various types of friction clutches. However, dog clutches have the known disadvantage of being engagable only while the shafts are stationary or rotating at a very low rate. Such clutches, however, can become disengaged during rotation. Friction clutches constitute the largest group of disengaging clutches and generally effect torque transfer by means of friction. However, such friction clutches are not entirely satisfactory in that slippage can occur between the driving and driven shafts during engagement of the clutch or when the driven shaft is in an overloaded condition. Such slippage results in deleterious heating of the clutch elements. The most widely known friction clutch is the disc clutch which finds use generally in automobile transmission apparatus, machine tools, etc. Another type of friction clutch is the so-called conical clutch which is used predominately in industrial applications as well as in vehicles to a somewhat lesser extent. Drum clutches having friction surfaces in the form of cylinders are also known.
With respect to self-actuating clutches, these conventionally include starting clutches, safety clutches and reversing clutches. Since the torque required in the initial start-up of machines is generally several times larger than the torque required to maintain a steady state rotation thereof, the particular start-up torque requirements depending upon the available time for start-up, it is usually not economical or otherwise practical to design the prime mover and power or torque transmission apparatus on the basis of the required start-up torque. In such cases, so-called starting clutches are utilized which are designed to allow the motion of the shafts to reach their highest desirable rotational speed.
The coupling and clutches described above, including the disengaging clutches, elastic couplings and movable couplings, are not entirely satisfactory. Thus, conventional mechanical couplings and clutches, e.g. geared couplings and/or dog clutches are disadvantageous in that they cannot operate in a stepless manner, i.e., as a stepless clutch. Conventional stepless clutches, such as so-called fluid clutches or torque converters, however, are relatively complex in design and are therefore expensive in manufacture. Such fluid clutches require the use of fluid seals which tend to wear during use requiring periodic replacement or servicing. As mentioned above, friction clutches have the drawback that slippage between the driving and driven shafts is not uncommon which causes wear thereby requiring frequent servicing.